Abstract 799: Hypoxia Regulates microRNAs Expression
Background. MicroRNAs (miRNAs) are an abundant class of small non-protein-coding RNAs that function as negative gene regulators. Through specific base-pairing with mRNAs, these approximately 22-nt RNAs induce mRNA degradation or translational repression, or both. They regulate diverse biological processes, and each miRNA can control hundreds of gene targets, underscoring the potential influence of miRNAs on almost every genetic pathway. More than 300 miRNA have identified so far in humans, but bioinformatic data predict that several hundred more may exist, suggesting a pervasive regulatory role in most physio-patological processes. The aim of the present study was assessing miRNAs regulation and functional role in endothelial cell response to hypoxia.
Methods and Results. Human Umbelical Vein Endothelial Cells (HUVEC) were exposed to hypoxia (1% O2) for 0, 8, 24 and 48 hrs inducing growth arrest and cell death. At 48 hrs, only few cells incorporated BrdU and cell number was 53%±7 of T0 (p<0.0001). A selection of 183 miRNAs was measured using real-time PCR technique with TaqMan technology (n=4). This assay was designed to detect and accurately quantify only mature miRNAs. We found that 153 miRNAs were detectable in HUVEC and 5 of them were modulated more than 5 fold (p=0.002). The expression of miRNA 210, 150 and 328 progressively increased upon exposure to hypoxia and it was 40±1, 23±1 and 15±1 fold higher than control, respectively (p<0.0001). Interestingly, miRNA 184 expression peaked at 8 hrs (12±1 fold induction, p<0.002) and decreased thereafter. Finally, miRNA 7 expression progressively decreased following exposure to hypoxia and it was 8±1 fold lower than control at 48 hrs (p<0.002). We confirmed miRNA 210 up-regulation by northern blotting and we found that miRNA 210 induction by hypoxia was not limited to endothelial cells since it was observed in U2OS osteosarcoma cells as well.
Conclusions. Hypoxia regulates the expression of specific miRNAs, suggesting that these may play a role in the physio-pathological responses of endothelial cells to ischemia.